1. Field of the Invention
The invention relates to image processing apparatus and method having a function to add additional information to an input image and relates to a storage medium in which such a method has been stored.
2. Related Background Art
In recent years, the performance of an image processing apparatus such as color printer, color copying apparatus, or the like has been improved and an image of a high picture quality can be provided. Thus, an image can be being formed with a picture quality almost similar to that of a bill, securities, or the like.
However, the formation of such an image is inhibited and it is necessary to suppress such illegal behavior. As one of countermeasures for this purpose, there has been known a technique to bury a dot pattern showing the numbers (information such as manufacturing number, product number, user ID, and the like) which are peculiar to the image processing apparatus into each image to be formed. By performing such a process, even if an image is illegally formed, by analyzing the dot pattern buried in the formed image, various situations at a time when the image is formed can be also known.
The dot pattern is periodically buried into the whole image every predetermined periods. Therefore, even if only a part of the image exists, since the information has been buried in this partial portion, the search of the various information as mentioned above can be executed.
To perfectly search the various information, an area of the partial portion in the image needs to be set to an area corresponding to at least one period among the above periods.
A conventional adding method of the dot pattern (additional information) as mentioned above differs every manufacturer who manufactures each of the image processing apparatus. To decode the additional information such as a manufacturing number and the like on the basis of a certain formed image, it is necessary to sequentially use a decoding method corresponding to the adding method of each manufacturer.
However, hitherto, there is a problem such that the additional information (manufacturing number, product number, user ID, and the like) added to the image which is finally formed cannot be decoded at all due to a cause such that the image process of the input image has some periodic trouble, the original image contents are periodic, or the like.
Particularly, the problem as mentioned above is likely to occur in the case where an area of the formed image is small like a stamp or the like rather than the case where an area of the formed image is large like a bill or the like.
Hitherto, in the case where the number of manufacturers who manufacture the apparatuses is large, there is a problem such that a load to sequentially use the decoding methods as mentioned above is large. In particular, such a problem typically appears in case of performing the above decoding by a software process or the like.